During the third week of development conceptus implantion in the uterus wall is complete and trophoblast cells continue to invade uterine wall in the process of early placentation (villi formation). Within the conceptus, gastrulation converts the bilaminar embryo into the trilaminar embryo (ectoderm, mesoderm, endoderm). Morphological changes include an epithelial to mesenchymal cell transition and folding of the the embryonic disc. Carnegie stages 7 to 9 covers this period of human embryo development (More? Development Overview).
EM of Primitive Streak and Primitive Node Inside the embryo, axial process formation (notochord), mesoderm differentiation (somites, heart, vascular) ectoderm differentiation (neuralation) have begun (More? System Notes). |
Human Carnegie Stage 7 embryo Dorsal view of the embryonic disc showing the connecting stalk and the primitive streak (dark stripe), the site of gastrulation. |
Outside of the embryo, the extraembryonic spaces (chorionic, amniotic, yolk) and intraembryonic spaces (coeloms) continue to develop (More? Coelom). Trophoblast cells continue to invade uterine wall and the emdometrium is being converted into the decidua, the process of villi formation and early placentation has begun (More? Placenta). |
Page Links: Introduction | Some Recent Findings | Reading | Objectives | Computer Activities | Development Overview | Molecular Factors | References | Glossary
Related Pages: Abnormalities | Gastrulation | Trilaminar Embryo | Neural Tube Formation | Early Somite Formation | Developmental Mechanisms | Epithelial Mesenchymal Transition | Molecular Development | References | Text only page | WWW Links |
Sweetman D, Wagstaff L, Cooper O, Weijer C, Munsterberg A. The migration of paraxial and lateral plate mesoderm cells emerging from the late primitive streak is controlled by different Wnt signals. BMC Dev Biol. 2008 Jun 9;8(1):63.
"...we use long-term video microscopy in chicken embryos to visualize the migration routes and movement behaviour of mesoderm progenitor cells as they emerge from the primitive streak (PS) between HH stages 7 and 10."
Skoglund P, Rolo A, Chen X, Gumbiner BM, Keller R. Convergence and extension at gastrulation require a myosin IIB-dependent cortical actin network. Development. 2008 Jun 11.
"...Xenopus laevis, a system in which the polarized cell motility that drives this active cell intercalation has been related to the development of forces that close the blastopore and elongate the body axis, to examine the role of myosin IIB in convergence and extension. We find that myosin IIB is localized in the cortex of intercalating cells"
UNSW Embryology: Lecture 2004 ANAT2300 Vertebrate Development- Week 3 | Lecture 2003 Medicine ANAM1006- Week 3 | Lecture 2002 ANAT1006 Medicine- Week 3 | Abnormalities | Gastrulation | Trilaminar Embryo | Neural Tube Formation | Early Somite Formation | Text only page | WWW Links | 10 to 14 Images - formation of the axial process | 16 to 19Images - mesoderm and body cavities | 20 to 23- the yolk sac and gut formation | 24 to 25- mesoderm differentiation
UNSW Embryology Movies:Gastrulation (272Kb) | Notochord (179Kb) | Notochord (111Kb) | Neural Plate (468Kb)
Embryo Images Unit: Embryo Images Online Unit: Early cell Populations | Early Cell Populations and Establishment of Body Form | Germ Layers and Initial Gastrulation (Week 3) | Form Changes (Week 3) | Neural Crest
Week 3 (Clinical Week 5)
Day |
Stage |
Event |
15 |
||
16 |
Stage 7 |
  |
17 |
||
18 |
Stage 8 |
Neural – neurogenesis, neural groove and folds are first seen |
19 |
 |
|
20 |
Stage 9 |
Musculoskeletal – somitogenesis, first somites form and continue to be added in sequence caudally Neural – the three main divisions of the brain, which are not cerebral vesicles, can be distinguished while the neural groove is still completely open Neural Crest – mesencephalic neural crest is visible (PMID: 17848161) |
21 |
Heart – cardiogenesis, week 3 begins as paired heart tubes. |
(More? Development - Weeek by Week | Development - Weeek by Week Detailed)
The factors listed below have been shown in various animal models to have roles in the developmental processes occuring during the equivalent of Human Week 3. Note that numbers in brackets are the PubMed reference ID.
Gastrulation
Links: Textbooks | Online Textbooks | Search Textbooks | Reviews | Articles | Search PubMed | Glossary
Specific references can also be found on each notes page and Selected References 1999
Human Embryology (2nd ed.) Larson Chapter 1 p1-32
The Developing Human: Clinically Oriented Embryology (8th ed.) Moore and Persaud, Chapter 3 pp42-53
Before we Are Born (5th ed.) Moore and Persaud Chapter 4 pp47-61
Essentials of Human Embryology Larson Chapter 1 p1-16
Human Embryology Fitzgerald and Fitzgerald
UNSW Embryology Selected Week 3 References
Developmental Biology (6th ed) Gilbert, Scott F. Sunderland (MA): Sinauer Associates, Inc.; c2000. Figure 11.24. Implantation of the mammalian blastocyst into the uterus | Early Mammalian Development
Search NLM Online Textbooks "blastocyst implantation" : Developmental Biology | Endocrinology | Molecular Biology of the Cell | The Cell- A molecular Approach
Reviews
von Dassow M, Davidson LA. Variation and robustness of the mechanics of gastrulation: the role of tissue mechanical properties during morphogenesis. Birth Defects Res C Embryo Today. 2007 Dec;81(4):253-69.
Rohde LA, Heisenberg CP. Zebrafish gastrulation: cell movements, signals, and mechanisms. Int Rev Cytol. 2007;261:159-92.
Nance J, Lee JY, Goldstein B. Gastrulation in C. elegans. WormBook. 2005 Sep 26:1-13.
Kodaman PH, Taylor HS Hormonal regulation of implantation. Obstet Gynecol Clin North Am. 2004 Dec;31(4):745-66, ix.
Articles
Pézeron G, Mourrain P, Courty S, Ghislain J, Becker TS, Rosa FM, David NB. Live analysis of endodermal layer formation identifies random walk as a novel gastrulation movement. Curr Biol. 2008 Feb 26;18(4):276-81.
Nakaya Y, Sukowati EW, Wu Y, Sheng G. RhoA and microtubule dynamics control cell-basement membrane interaction in EMT during gastrulation. Nat Cell Biol. 2008 Jun 15.
Yao S, Xie L, Qian M, Yang H, Zhou L, Zhou Q, Yan F, Gou L, Wei Y, Zhao X, Mo X. Pnas4 is a novel regulator for convergence and extension during vertebrate gastrulation. FEBS Lett. 2008 Jun 25;582(15):2325-32.
Sweetman D, Wagstaff L, Cooper O, Weijer C, Munsterberg A. The migration of paraxial and lateral plate mesoderm cells emerging from the late primitive streak is controlled by different Wnt signals. BMC Dev Biol. 2008 Jun 9;8(1):63.
Güney M, Erdemoglu E, Oral B, Karahan N, Mungan T. Leukemia inhibitory factor (LIF) is immunohistochemically localized in tubal ectopic pregnancy. Acta Histochem. 2008 Feb 6;
Alisch RS, Jin P, Epstein M, Caspary T, Warren ST. Argonaute2 is essential for mammalian gastrulation and proper mesoderm formation. PLoS Genet. 2007 Dec 28;3(12):e227.
Hu W, Feng Z, Teresky AK, Levine AJ. p53 regulates maternal reproduction through LIF. Nature. 2007 Nov 29;450(7170):721-4.
Ralston A, Rossant J. How signaling promotes stem cell survival: trophoblast stem cells and shp2. Dev Cell. 2006 Mar;10(3):275-6.
Yang W, Klaman LD, Chen B, Araki T, Harada H, Thomas SM, George EL, Neel BG. An Shp2/SFK/Ras/Erk Signaling Pathway Controls Trophoblast Stem Cell Survival. Dev Cell. 2006 Mar;10(3):317-27.
Search Feb 2008 "blastocyst implantation" 7,336 reference articles of which 1,029 were reviews.
Search PubMed: term = week 3 embryonic human development | gastrulation | somite formation |
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Week 3 of human development is mainly about the development of the trilaminar embryo, extraembryonic spaces and continued implantation with early placentation.
Coeloms are spaces or cavities.
Please email Dr Mark Hill if you wish to make a comment about this current project.
